U.S. patent number 9,254,153 [Application Number 14/172,161] was granted by the patent office on 2016-02-09 for hip fracture device with static locking mechanism allowing compression.
This patent grant is currently assigned to Stryker Trauma GmbH. The grantee listed for this patent is Stryker Trauma GmbH. Invention is credited to Carsten Hoffmann, Jakob Kemper, Bernd Simon.
United States Patent |
9,254,153 |
Simon , et al. |
February 9, 2016 |
Hip fracture device with static locking mechanism allowing
compression
Abstract
In one embodiment, the present invention is a method of fusing
fractures of a femoral neck using a bone plate including the steps
of: placing a bone plate on the femur; inserting an assembly of a
bone screw and a locking ring in an opening in the plate;
simultaneously threading the locking ring and the bone screw in the
femur; threading the bone screw in the femur to compress the
fracture; creating a space between the locking ring and the bone
screw; and allowing the bone screw to move towards the locking ring
when the femur is loaded. In another embodiment, the present
invention is a bone plating system including a bone plate having a
plurality of openings; at least one bone screw capable of being
received through the opening and into a bone; at least one end cap
fixedly insertable in the opening; and a layer of polymeric
material interposed between the end cap and the top of the
head.
Inventors: |
Simon; Bernd (Kiel,
DE), Kemper; Jakob (Santiago, CL),
Hoffmann; Carsten (Monkeberg, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Stryker Trauma GmbH |
Schonkirchen |
N/A |
DE |
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Assignee: |
Stryker Trauma GmbH
(DE)
|
Family
ID: |
39620331 |
Appl.
No.: |
14/172,161 |
Filed: |
February 4, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140148861 A1 |
May 29, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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12082689 |
Apr 11, 2008 |
8734494 |
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60925457 |
Apr 19, 2007 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
17/8042 (20130101); A61B 17/746 (20130101); A61B
17/74 (20130101); A61B 17/8685 (20130101) |
Current International
Class: |
A61B
17/70 (20060101); A61B 17/04 (20060101); A61B
17/74 (20060101); A61B 17/86 (20060101); A61B
17/80 (20060101) |
Field of
Search: |
;606/65-66,280-299,104,300-331,246-279 |
References Cited
[Referenced By]
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2007138062 |
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Dec 2007 |
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WO |
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Other References
Osteon News 39 Brouchre, Comprehension Hip Screw. cited by
applicant.
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Primary Examiner: Beccia; Christopher
Attorney, Agent or Firm: Lerner, David, Littenberg, Krumholz
& Mentlik, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
The present application is a divisional of U.S. patent application
Ser. No. 12/082,689, filed Apr. 11, 2008, which claims the benefit
of the filing date of U.S. Provisional Patent Application No.
60/925,457 filed Apr. 19, 2007, the disclosure of which is hereby
incorporated herein by reference.
Claims
The invention claimed is:
1. A method of fusing fractures of a femoral neck using a bone
plate comprising the steps of: placing a bone plate on the femur;
inserting an assembly of a bone screw and a locking ring in an
opening in the plate; simultaneously threading the locking ring and
the bone screw in the femur; threading the bone screw in the femur
to compress the fracture; creating a space between the locking ring
and the bone screw; allowing the bone screw to move towards the
locking ring when the femur is loaded; and removing the locking
ring and the bone screw by simultaneously rotating the locking ring
and the bone screw using a dedicated instrument.
2. The method of claim 1, further comprising the step of; stopping
further axial movement of the bone screw upon the screw head
contacting the locking ring.
Description
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates generally to an apparatus and method
for the treatment of fractures of the proximal femur including the
neck of the femur and the intertrochantric region.
2. Brief Description of the Prior Art
In treatment of the fracture of the femoral neck it is necessary to
maintain angular stability of the head fragment to maintain an
anatomical reduction postoperatively. It is also desirable to
compress fracture site intra-operatively and then to stabilize the
bone fragments by not allowing any further axial or angular
movement. Since axial movement of the bone fragment resulting in
shortening of the neck of the femur will result in reduced physical
functioning, particularly in younger patients, it is desirable to
stabilize the fracture postoperatively.
Many locking plates are available that allow stabilization of bone
fragments. Conventional locking plates (also known as bone plates)
have a plate that is attached to the fragments of the fractured
bone via screws that are inserted in the bone through screw holes
in the plate. The screws of the conventional locking plates have
threads on the head portion in addition to the threads on the
shaft. The threads on the head portion have a greater core diameter
than the threads on the shaft but both threads have same pitch.
When the screw is advanced in the bone and the head of the screw is
in the screw hole of the bone plate, the threads on the screw head
engage matching threads in the screw hole. This locks the screw in
place and prevents it from moving in the axial direction post
operatively. However, such bone plate system cannot be used to
compress the fracture site. In another conventional bone plate
system used for femoral neck fracture a compression screw is used.
The compression screw head does not have the threads and therefore
may be rotated further after its head has reached the final axial
position thereby compressing the fracture site. A separate end cap
is then screwed in the compression screw hole of the bone plate to
prevent the screw from moving back in the axial direction.
These bone plate systems require a separate step of installing an
end cap to prevent post operative axial movement of the screw.
Therefore, there is a need for further improvement in bone plate
systems to provide an easy to use plate system that facilitates
intra-operative compression and at the same time provides angular
and axial stability post operatively.
As used herein, when referring to bones or other parts of the body,
the term "proximal" means closer to the heart and the term "distal"
means more distant from the heart. The term "inferior" means toward
the feet and the term "superior" means towards the head. The term
"anterior" means towards the front part of the body or the face and
the term "posterior" means towards the back of the body. The term
"medial" means toward the midline of the body and the term
"lateral" means away from the midline of the body.
SUMMARY OF THE INVENTION
The present invention provides a bone plate for use with fractures
of the femur. Screws attach the bone plate to the femur. The
compression screws that are inserted in the neck of the femur may
be parallel to the axis of the neck of the femur. Inserting the
bone screws in the neck region of the femur provides compression
and angular and rotational stability to the head of the femur.
Cortical interlocking type screws may be used in a distal portion
of the bone plate in the subtrochantric shaft region of the femur.
The compression screws stabilize bone fragments when used with end
caps and prevent the shortening of the femoral neck resulting in
improved postoperative function of the hip. The end cap may be
inserted in a threaded plate hole and contact the top of each
screw. A polymer buffer may be placed in the screw hole between the
end cap and the head of the compression screw. The polymer buffer
may allow small movement of the screw.
In use, the compression bone screw is inserted in the screw hole
and screwed into the neck of the femur until the underside of the
bone screw sits on the flat face formed in screw hole. Next, the
screw is rotated further to apply compression to the fracture site.
Once the desired amount of compression is applied, the end cap is
inserted in screw hole. The end cap prevents the screw from moving
back in the axial direction.
In another embodiment, a compression screw having a different head
design is used with a split locking ring. The locking ring has a
smooth circular outer surface that fits in the screw hole. The
inner surface of the locking ring has a saw blade like or similarly
functioning geometry. The saw blade geometry on the inner surface
is preferably asymmetric. The compression screw head has a saw
blade geometry that can mate with the saw blade geometry on the
inner surface of the locking ring.
In use, the screw and the split locking ring are assembled together
and inserted into the screw hole. The assembly of the screw and the
locking ring is then screwed into the bone using a dedicated
insertion instrument that holds and rotates the screw and the
locking ring simultaneously. When the head of the screw reaches the
terminal axial position in the screw hole, both the screw and the
locking ring can be rotated further to apply compression to the
fracture site. After the compression is applied, the screw alone is
turned. The locking ring is thereby clamped between the head of
screw and the bone plate. This results in fixing the screw in place
such that the screw can not back out in axial direction.
In yet another embodiment, a compression screw having a different
head design is used with a locking ring. The locking ring has a
threaded circular outer surface that fits in the screw hole. The
top wall of the locking ring projects towards the center of the
screw hole and has a hexagonal internal periphery. The bottom
surface of the top wall has ridges. The screw has a head that has
an outer peripheral surface that slidably fits into the locking
ring. The top surface of the head of the screw has depressions that
correspond to the ridges. Thus, when the screw is assembled in
locking ring, the ridges sit in the depressions. The top surface of
the screw head also has a hexagonal depression to allow engagement
of a suitable screw driver.
In use, the compression screw and the locking ring are assembled
together and inserted into the screw hole. The assembly of the
screw and the locking ring is then screwed into the bone using a
dedicated insertion instrument that holds and rotates the screw and
the locking ring simultaneously. When the head of the screw reaches
the terminal axial position in the screw hole, the screw can be
rotated further to apply compression to the fracture site. When the
screw is rotated further the ridges loose contact with the
depressions. This forms a small gap of approximately 0.1-0.4
millimeters between the screw and the locking ring. As soon as the
body weight is applied post-operatively, the femoral head fracture
fragment presses the screw back to the lateral side until the
movement is stopped by the locking ring. The polymer buffer may
also be used with any of the above described embodiments.
In one aspect the present invention provides a bone plating system
having a bone plate having a plurality of openings. The system
includes at least one bone screw for insertion in the opening and
into a bone and having a head. Depressions are formed on a top
surface of the head, and a locking ring adapted to attach to the
head and having ridges that have shape complimentary to the
depressions is provided. The locking ring fits in the depressions
when the locking ring is attached to the head. The locking ring and
the bone screw are assembly together and simultaneously inserted in
the opening using a dedicated instrument.
In another aspect, a bone plating system includes a bone plate
having a plurality of openings. The system also has at least one
bone screw capable of being received through the opening and into a
bone. The head of the bone screw has an asymmetric saw blade
geometry formed on the periphery. A locking ring having an
asymmetric saw blade geometry matching the asymmetric saw blade
geometry formed on the periphery of the head is provided. The
locking ring and the bone screw are assembly together such that the
saw blade geometry on the locking ring is in engagement with the
saw blade geometry on the head, and the assembly is inserted in the
opening using a dedicated instrument.
In yet another aspect, a bone plating system includes a bone plate
having a plurality of openings and at least one bone screw capable
of being received through the opening and into a bone. The bone
screw having a head adapted for fitting in the opening when the
bone screw is fully inserted in the bone, the head of the bone
screw and the opening in the bone plate having complementary shape
such that the bone screw when seated in the opening has angular
stability. At least one end cap is fixedly inserted in the opening,
and a layer of polymeric material is interposed between the end cap
and the top of the head such that the compression of the polymeric
material would allow slight axial movement of the screw.
In yet another aspect, a method of fusing fractures of femoral neck
using a bone plate is disclosed. The method includes placing a bone
plate on the femur, and inserting an assembly of a bone screw and a
locking ring in an opening in the plate. Thereafter, simultaneously
threading the locking ring and the bone screw in the femur and
further threading the bone screw in the femur to compress the
fracture. A space is created between the locking ring and the bone
screw allowing the bone screw to move towards the locking ring when
the joint is loaded.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an anterior elevation view of a bone plate mounted on a
femur.
FIG. 1A shows another embodiment of a bone plate that may be
mounted on the femur.
FIG. 2 shows an isometric sectional view of a screw hole in the
bone plate of FIG. 1 with a bone screw and an end cap inserted
therein.
FIG. 3 is an isometric view of a first locking ring embodiment.
FIG. 4 shows a sectional view of the bone plate of FIG. 1 with a
locking ring and a screw installed therein.
FIG. 5 is a lateral view of a portion of a bone plate assembly
showing the bone plate, a screw and the locking ring of FIG. 3.
FIG. 6 is a sectional view of the bone plate of FIG. 1 with a
second embodiment of a locking ring and a screw installed
therein.
FIG. 7 is another sectional view of the embodiment of FIG. 6.
DETAILED DESCRIPTION
FIG. 1 shows a bone plate 20 mounted on a femur 22. Any one of the
compression screws disclosed hereafter may be used with the bone
plate 20. In FIG. 1, compression screws 24A attach the bone plate
20 to the head 33 and neck 31 of femur 22. Screws 24A may be used
to attach bone plate 20 to the femur via screw holes 26 in plate
20. Cortical screws 25 may be used to attach a distal portion 27 of
bone plate 20 to the subtrochantric shaft of the femur 22. In the
preferred embodiment these are locking screws. The compression
screw 24A may provide angular and axial stability to the fractured
bone pieces. The compression screws 24A may be cannulated or
non-cannulated. The compression screws 24A may also provide
rotational stability. Rotational stability may be achieved by
inserting at least two compression screws 24A through the screw
holes 26 and into the neck 31 of the femur 22. The compression
screws 24A that are inserted in the neck 31 of the femur 22 may be
parallel to the axis of the neck 31 of the femur 22. Cortical
interlocking type screws 25 may be used in plate holes 29 in the
subtrochantric shaft region of the femur 22. The cortical
interlocking screws 25 may have threads (not seen in the figures)
on the periphery of the head portion for engaging threads in hole
29. The cortical interlocking type screws 25 may be used to prevent
the backout of the screws 25 and the bone plate 20. The compression
screws 24A stabilize the neck fracture head fragment and thereby
prevent the shortening of the femoral neck 31 resulting in improved
postoperative function of the hip. FIG. 1A shows a plate 20A. Plate
20A is a variation of design of plate 20, and includes a slot 21. A
guide wire may be inserted through slot 21 and into the head 33 of
femur 22. The guide wire may be used to position the plate 20A in a
desired alignment on the surface of the femur 22. Any one of the
compression screws disclosed hereafter may be used with the bone
plate 20A.
FIG. 2 shows the screw hole 26 in the bone plate 20 with bone
compression screw 24 and an end cap 28 inserted in the screw hole
26. The bone compression screw 24 may be a cannulated screw.
However, non-cannulated screws may also be used. In a preferred
embodiment, the screw hole 26 has a first threaded section 30
having a larger diameter and a second section 32 having a smaller
diameter. A flat face 34 is formed at the junction of the first
threaded section 30 and the second section 32. Threads (not seen in
the figures) may be formed on all or portion of the inner periphery
of the first threaded section 30. Inserting one bone compression
screw 24 in the neck region of the femur 22 provides angular
stability to the head 33 of the femur 22. One or two or three or
more bone compression screws 24 may be inserted in the neck region
of the femur 22. Inserting more than one bone compression screw 24
provides rotational stability to the head 33 of the femur 22. An
end cap 40 may be inserted in screw hole 26 on top of each
compression screw 24. A polymer buffer 44 may be placed in the
screw hole 26 between the end cap 40 and the head of the
compression screw 24. The polymer buffer 44 may allow small
movement of the compression screw 24.
In use, the bone compression screw 24 is inserted in the screw hole
26 and screwed into the neck 31 of the femur 22 until the underside
of the bone compression screw 24 sits on the flat face 34 formed in
screw hole 26. Next, the compression screw 24 is rotated further to
apply compression to the fracture site. Once desired amount of
compression is applied, the end cap 40 is inserted in screw hole
26. End cap 40 has threads (not seen in the figures) on its
periphery that mate with the threads in the screw hole 26. End cap
40 is screwed into the screw hole 26 till its bottom is on top of
the top surface of the head of the compression screw 24 that was
previously installed in that screw hole 26. Thus, the end cap 40
prevents the compression screw 24 from moving back in the axial
direction. Optionally, the polymer buffer 44 may be placed over the
compression screw 24 prior to installing the end cap 40. Cortical
bone screw 25 are also installed in screw holes 29 and screwed into
the subtrochantric shaft region of the femur 22. The screws 24 and
25 stabilize the bone fracture. The end cap 40 and the bone plate
20 also provide angular stability.
In another embodiment a compression screw 50 of a different head
design is used with a split locking ring 52. FIG. 3 shows the
locking ring 52. FIG. 4 shows a cross sectional view of the bone
plate 20 with the locking ring 52 and the compression screw 50
installed therein. FIG. 5 is a top view of a portion of a bone
plate assembly showing the bone plate 20, the compression screw 50
and the locking ring 52. The locking ring 52 has a smooth circular
outer surface 54 that fits in the screw hole 26. The inner surface
56 of the locking ring 52 has a saw blade like geometry. The saw
blade geometry on the inner surface 56 is asymmetric. The
compression screw 50 has a head 58 that has an outer peripheral
surface 60 with a saw blade geometry that can mate with the saw
blade geometry on the inner surface 56 of the locking ring 52. The
top surface 62 of the screw head 58 has a hexagonal depression to
allow engagement of a suitable screw driver. Other known shapes for
the depression and corresponding screwdriver may also be used.
In use, the compression screw 50 and the split locking ring 52 are
assembled together and inserted into the screw hole 26. The
assembly of the compression screw 50 and the locking ring 52 is
then screwed into the bone using a dedicated insertion instrument
that holds and rotates the compression screw 50 and the locking
ring 52 simultaneously. When the head of the compression screw 50
reaches the terminal axial position in the screw hole 26, both the
compression screw 50 and the locking ring 52 can be rotated further
to apply compression to the fracture site. After the compression is
applied, the compression screw 50 alone is turned. This makes the
compression screw 50 rotate in relation to locking ring 52 which
results in partial disengagement of saw blade geometry on the inner
surface 56 of the locking ring 52 from the saw blade geometry on
the outer peripheral surface 60. Since the saw blade geometries on
both these surfaces are asymmetrical, the disengagement results in
spreading of the locking ring 52. The locking ring 52 is thereby
clamped between the head of compression screw 50 and the bone plate
20. This results in fixing the compression screw 50 in place such
that the compression screw 50 can not back out in axial direction.
To remove the compression screw 50, compression screw 50 is rotated
in the opposite direction. This results in the engagement of the
saw blade geometries on the on the inner surface 56 of the locking
ring 52 and the outer peripheral surface 60. Next, the compression
screw 50 and the locking ring 52 may be removed simultaneously
using the dedicated instrument.
In yet another embodiment a compression screw 70 of a different
design is used with a locking ring 72. FIGS. 6 and 7 show the bone
plate 20, compression screw 70 and the locking ring 72 assembled
together. The locking ring 72 has a threaded circular outer surface
74 that fits in the screw hole 26. The top wall 76 of the locking
ring 72 projects towards the center of the screw hole 26 and has a
hexagonal internal periphery. The bottom surface 78 of the top wall
76 has ridges 80. The compression screw 70 has a head 82 that has
an outer peripheral surface 84 that slidably fits into the locking
ring 72. The top surface 86 of the head of the compression screw 70
has depressions 87 that correspond to the ridges 80. Thus, when the
compression screw 70 is assembled in locking ring 72, the ridges 80
sit in the depressions 87. The top surface 86 of the screw head 82
also has a hexagonal depression to allow engagement of a suitable
screw driver. Other known shapes for the depression and
corresponding screwdriver may also be used. The external surface of
the locking ring 72 may have threads (not seen in the figures) that
engage threads in the screw hole 26.
In use, the compression screw 70 and the locking ring 72 are
assembled together and inserted into the screw hole 26. The
assembly of the compression screw 70 and the locking ring 72 is
then screwed into the bone using a dedicated insertion instrument
that holds and rotates the compression screw 70 and the locking
ring 72 simultaneously. When the head of the compression screw 70
reaches the terminal axial position in the screw hole 26, the
compression screw 70 can be rotated further to apply compression to
the fracture site. When the compression screw 70 is rotated further
the ridges 80 loose contact with the depressions 87. This forms,
for example, a small gap of approximately 0.1-0.4 millimeter
between the compression screw 70 and the locking ring 72. As soon
as the body weight is applied post-operatively, the femoral head
fracture fragment presses the compression screw 70 back to the
lateral side until the movement is stopped by the locking ring
72.
To remove the compression screw 70, compression screw 70 is rotated
in the opposite direction. This results in the engagement of the
ridges 80 in the depressions 87. Next the compression screw 70 and
the locking ring 72 may be removed simultaneously using the
dedicated instrument.
Although the invention herein has been described with reference to
particular embodiments, it is to be understood that these
embodiments are merely illustrative of the principles and
applications of the present invention. It is therefore to be
understood that numerous modifications may be made to the
illustrative embodiments and that other arrangements may be devised
without departing from the spirit and scope of the present
invention as defined by the appended claims.
* * * * *